Linear motion bearing segment

ABSTRACT

A linear motion bearing assembly ( 20 ) as provided for movement along a splined shaft ( 10 ). The rolling element retainer of the bearing assembly ( 20 ) is assembled from a plurality of arcuate interengageable self-contained rolling element retainer segments ( 22 ). Each of the rolling element retainer segments ( 22 ) includes at least one rolling element track ( 30 ) having a load bearing portion ( 34 ) and a return portion ( 36 ). At least one load bearing plate ( 44 ) is axially positioned in each segment and serves to receive and transmit loads from the bearing rolling elements ( 32 ) in the load bearing portion ( 34 ) of the ball tracks ( 30 ). An extended housing retainer structure encloses all of the exposed exterior surfaces of the rolling element retainer segments ( 22 ) and is configured and dimensioned to maintain the rolling element retainer segments ( 22 ) in position and to receive a load either directly or indirectly from the load bearing plates ( 44 ).

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. provisionalapplication Serial No. 60/242,850 filed on Oct. 24, 2000, the entirecontents of which are hereby incorporated by reference.

BACKGROUND

[0002] 1. Technical Field

[0003] The present invention relates to linear motion bearing and, moreparticularly, to linear motion bearing assemblies made up of bearingsegments for longitudinal movement along a splined shaft.

[0004] 2. Background of Related Art

[0005] The present invention is directed to an improved linear motionbearings assembly for use on a splined shaft. In particular, theimprovements relate to biased linear motion bearing assemblies of thetype which support a carriage or a pillow block for linear movementalong an elongated splined shaft. These bearing assemblies can either beof the open type or the closed type.

[0006] Typical linear rolling bearing assemblies include a series ofrolling elements moving about a circulation path which circulation pathis formed in the periphery of a track member and a surrounding andenclosing bearing cover confining the rolling elements in theirrecirculation path. In order to achieve an accurate linear motion, theaxis of the bearing assembly must be precisely aligned with the desireddirection of motion along the supported structure. In addition thisprecise alignment also minimizes skewing forces acting on the bearingassembly, which skewing forces tend to reduce the load/life performanceof the bearing assembly.

[0007] Installation of such bearing assemblies on a supporting structure(i.e., shaft, splined shaft, guideway or rail) typically involvesprecision machining of locating surfaces in order to properly align thebearing assembly on the supporting structure. Such bearing assembliesare typically installed in sets, each comprised of a number of variouslyfacing bearings such as to engage a series of surfaces on the supportingstructure (i.e., such as above and below a supporting surface and/oralong a lateral edge of a supporting surface). In such instances it isusual to provide a bearing adjustment for enabling precision adjustmentof the bearing assembly on the supported structure and also forestablishing a proper bearing pre-load by adjusting an opposing bearingassembly for reasons well known to those skilled in the art. In suchinstallations, considerable precision machining of the supportedstructure is necessitated which is difficult and expensive to accomplishon the supporting structures.

[0008] Additional prior art bearing assemblies typically include anouter housing and at least one ball retainer dimensioned for insertioninto the outer housing. The rolling element retainer has at least oneball track in a loop configuration for containing and recirculatingbearing balls therein. The ball tracks typically include open portionswhich facilitate a load transfer from a supporting shaft to a loadbearing structure such as load bearing plates operatively associatedwith either the ball retainer or the outer housing while return portionsof the ball tracks permit continuous recirculation of the bearing ballsthrough the ball tracks during linear motion.

[0009] In some embodiments, the ball retainer is formed as a monolithicelement with the ball tracks integrally incorporated therein. See, U.S.Pat. No. 3,767,276 to Henn. This structure, however, is difficult toefficiently manufacture because of the complex molds required. Also,these ball retainers, prior to insertion into a mounting carriage orouter housing are necessarily open and thus exposed to ambientconditions and contaminants such as dust and dirt. Such exposure coulddeleteriously affect the operation and life of the bearing assembly aswell as the support structure on which it moves.

[0010] Self-contained linear bearing units are also known in the art.See, e.g. U.S. Pat. No. 4,815,862 to Mugglestone et al. This unit, whilerepresenting a marked improvement in the art, still requires the use ofend caps to engage the load bearing plates of the bearing segments.Further, the load bearing plates must be precisely machined to properlyinter-fit with the end caps. This configuration adds to the expense andcomplexity of the bearing.

[0011] The load bearing structure may be in the form of integralelements formed on an inner radial surface of the outer housing. Typicalbearing assemblies utilizing load bearing structures formed in the outerhousing are shown, for example, in commonly owned U.S. Pat. No.5,046,862 to Ng, the disclosure of which is incorporated herein byreference.

[0012] In lieu of integral load bearing structure, separate load bearingplates may be used to transfer loads from the supporting shaft. Theseload bearing plates are longitudinally oriented in association with theball retainer so as to engage at least those bearing balls in directcontact with the support shaft. These load bearing plates may also beconfigured to be axially self-aligning by providing structure whichpermits the plates to rock into and out of parallelism with thelongitudinal axis of the ball retainer. See, for example, commonly ownedU.S. Pat. No. 3,545,826 to Magee et al. Individual load bearing platesmay be expanded transversely so as to engage bearing balls incorresponding adjacent load bearing tracks. In this form, parallelgrooves are formed in the underside of the plates to guide the bearingballs while they are in the load bearing portion of the ball tracks.See, for example, U.S. Pat. No. 3,951,472 to Schurger et al.

[0013] Accordingly, it is an object of the present invention to providea linear motion bearing segment which can be easily and efficientlymanufactured.

[0014] It is another object of the present invention to provide a linearmotion bearing assembly having a rolling element retainer and outerhousing which are easily fabricated using engineering polymers, powdermetal or insert molding.

[0015] It is a further object of the present invention to provide a lowcost linear motion bearing assembly having a high load bearing capacityand having self-aligning capability.

[0016] It is yet another object of the present invention to provide abearing assembly which eliminates the need for extremely high precisionrolling element/guideway (rail) bearing assemblies and their resultantexpensive manufacturing costs.

[0017] These and other highly desirable objects are accomplished by thepresent invention in a linear motion bearing assembly having a pluralityof rolling element tracks and individual bearing plates arranged in arolling element retainer and enclosed by a low cost outer housing whichserves to protect the rolling elements, rolling element tracks and loadbearing plates without having to transmit loads from the bearing rollingelements to the carriage block into which the bearing assembly ismounted.

[0018] Objects and advantages of the invention are set forth in partherein and in part will be obvious therefrom, or may be learned bypractice with the invention, which is realized and attained by means ofinstrumentalities and combinations pointed out in the appended claims.The invention comprises the novel parts, constructions, arrangements,combinations, steps, processes and improvements herein shown anddescribed.

SUMMARY OF THE INVENTION

[0019] The present invention provides for a linear motion bearingsegment configured and adapted for movement along a splined shaft,guideway or rail. A rolling element retainer structure of the bearingassembly can be either monolithically formed or, alternatively,assembled from multiple elements. In a first multi-element embodiment,the rolling element retainer structure is made up of a pair of quarterarcuate rolling element retainer segments and a half arcuate rollingelement retainer segment. In an alternate multi-element embodiment, therolling element retainer structure is made up of a pair of half arcuaterolling element retainer segments. At least a portion of the axialrolling element bearing tracks are formed in the rolling elementretainer structure and, preferably, the complete rolling element bearingtracks are formed therein.

[0020] The linear motion bearing assembly further includes an outerhousing sleeve which substantially encloses all of the rolling elementretainer structure. The housing sleeve is preferably formed of anengineering polymer and serves to protect the rolling element retainerand bearing rolling elements contained therein from ambientcontamination.

[0021] A plurality of load bearing plates are axially positioned withinthe outer housing and serve to receive and transmit loads from thebearing rolling elements to the load bearing portion of the rollingelement bearing tracks. Each load bearing plate is at least partiallyretained in the linear motion bearing assembly by retaining featureswhich are disposed at least partially around the rolling elementretainer structures and which retain at least a portion of the loadbearing plates. Preferably, the load bearing plates and/or plateretaining features are configured and dimensioned such that the linearmotion bearing assembly is substantially self-aligning on the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, referred to herein and constituting apart hereof, illustrate the preferred embodiments of the linear motionbearing segment of the present invention and, together with thedescription, serve to explain the principles of the invention.

[0023]FIG. 1 is an exploded perspective view of a linear motion bearingsegment, with the housing removed, in accordance with one embodiment ofthe present invention;

[0024]FIG. 2 is a transverse cross-sectional view of an assembled linearmotion bearing segment shown in FIG. 1;

[0025]FIG. 3 is an exploded perspective view of a half bearing segmentof the linear motion bearing segment shown in FIG. 1;

[0026]FIG. 4 is a perspective view of the linear motion bearing segmentwith the housing removed and in place in a splined shaft;

[0027]FIG. 5 is an end elevational view of the linear motion bearingsegment showing the internal elements of the bearing segment in phantom;

[0028]FIG. 6 is a transverse cross-sectional view of a linear motionbearing segment in accordance with a second embodiment of the presentinvention; and

[0029]FIG. 7 is an exploded perspective view of the half bearing segmentof the linear motion bearing segment shown in FIG. 6.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] Referring now to the drawings, wherein like reference numeralsidentify similar structural elements of the subject invention, there isillustrated in FIGS. 1-5 a closed-type linear motion bearing segmentconstructed in accordance with a preferred embodiment of the presentinvention and designated generally by the reference numeral 20. As usedherein, the term ball and rolling element are intended to be usedinterchangeably and encompass namely, ball bearings, roller bearings,needle bearings, axle bearings, etc. While a closed-type linear motionbearing segment is disclosed, it is envisioned that an open type linearmotion bearing segment can be constructed in accordance with the presentdisclosure.

[0031] Linear motion bearing segment 20 is fabricated from a pair ofindividual quarter arcuate interengageable self-contained ball retainersegments 22 and a half arcuate interengageable self-contained ballretainer segment 24 all of which are supported in interengageableassociation within a housing 26. The housing 26 includes a longitudinalgroove 18 formed along an inner surface thereof for engaging the halfarcuate retainer segment 24. Stated differently, the linear motionbearing segment 20 is fabricated from a pair of 90° arcuateinterengageable self-contained ball retainer segments 22 and a single180° arcuate interengageable self-contained ball retainer segment 24.When fully assembled, the quarter segments 22 and the half segment 24for a linear motion bearing segment 20 are adapted and configured tomove on a splined shaft 10 without rotational motion of the bearingsegment 20 relative to a longitudinal axis of the splined shaft 10.Further, although shown as a closed-type bearing, an open-type bearingcould be readily fabricated using such self-contained segments.

[0032] Each quarter segment 22 includes an inner portion 28 having aninner surface configured and adapted to be in clearance to the adjacentquarter arcuate portion of the outer surface of the splined shaft 10,the inner portion 28 defining a ball bearing track 30 formed therein andwhich ball bearing track 30 retains a plurality of bearing balls 32. Theball bearing track 30 is made up of a load bearing portion 34 and areturn portion 36 interconnected by turnarounds 38. An outer lid portion40 is adapted and configured to engage the inner portion 28 and includesa load bearing plate mounting aperture 42. By way of example only, theouter lid portion 40 can be snap fit into engagement with the innerportion 28. However, other engagement mechanisms, such as pins, grooves,adhesives, etc. are also contemplated and are within the scope ofknowledge of one skilled in this art.

[0033] A load bearing plate 44 is dimensioned and configured to fit intoaperture 42 of outer lid portion 40 of each quarter bearing 22. A pairof longitudinal grooves 46 are formed in the side walls of each loadbearing plate 44, which grooves 46 receive projections 48 formed in theperiphery of aperture 42. Each load bearing plate 44 preferably includesat least one longitudinal track 50 formed in an inner surface thereof.This longitudinal track 50 serves as the upper surface of the loadbearing portion 34 of the ball track 30. The plurality of bearing balls32 are positioned in ball track 30 and, when in the load bearing portion34, serve to transmit loads from the load bearing plates 44 to thesplined shaft 10 as well as to facilitate reciprocal longitudinal motiontherealong.

[0034] As seen in FIGS. 1 and 2, and in particular in FIG. 3, the halfarcuate ball retainer segment 24 includes a base portion 52 having aninner surface configured and adapted to be in substantial clearance ofspline 12 formed along a longitudinal length of the shaft 10. The baseportion 52 includes an outer surface defining a pair of independent ballbearing tracks 54 formed therein and which ball bearing tracks 54 retaina plurality of bearing balls 56. Each ball bearing track 54 is made upof a load bearing portion 58 and a return portion 60 interconnected byturnarounds 62. The respective load bearing portions 58 are locatedadjacent to one another and are spaced from one another by a retainingmember 64 formed longitudinally along the base portion 52.

[0035] The half arcuate ball retainer segment 24 further includes asingle load bearing plate 66 having an inner surface configured andadapted to be disposed over both load bearing portions 58 of each ballbearing track 54 and an outer surface defining a pair of longitudinallyextending convergent flat portions 68 and 70. Each convergent flatportion 68 and 70 is configured and adapted to engage a biasing spring72. In addition, the half arcuate ball retainer segment 24 furtherincludes a pair of lids 74 and 78, which lids 74 and 78 serve to closethe half retainer segment 24. Each lid 74 and 78 includes a window 80for receiving one of the convergent flats 68 and 70 respectively of theof the load bearing plate 66 and through which window 80 each biasingspring 72 can extend to contact the inner surface of the housing 26.(See FIG. 4)

[0036] In use, each biasing spring 72 applies a pre-load to the bearingballs 56 through each convergent flat 68 and 70 of the load bearingplate 66. The pre-load being applied against opposite sides 14 and 16 ofthe spline 12 at an angle “θ” in a range of between about 25° to about75°. (See FIG. 2). While the biasing spring 72 is shown as a corrugatedleaf spring, it is envisioned that other biasing springs may besubstituted including resilient plastic filler, coil springs, torsionsprings, etc., with corresponding adaptations to the housing and bearingplates.

[0037] Although shown herein in a half bearing segment configuration, itis also contemplated that other sizes can be used including quarters orthirds and that the segments can be arranged to accommodate multiplesplines on an elongate shaft.

[0038] Referring now to FIGS. 6 and 7, there is illustrated aclosed-type linear motion bearing segment constructed in accordance witha further embodiment of the present invention and designated generallyby the reference numeral 100. The linear motion bearing segment 100 isfabricated from a pair of individual half arcuate interchangeableself-contained ball retainer segments 102 supported in interengageableassociation within a housing 104. When fully assembled, the halfsegments 102 are adapted and configured to move on a splined shaft 106,having a substantially “I” shaped cross-section, without rotationalmotion of the bearing segment 100 relative to a longitudinal axis of thesplined shaft 106. Further, although shown as a closed-type linearbearing, an open-type linear bearing could be readily fabricated usingsuch self-contained segments.

[0039] Each half segment 102 includes an inner portion 108 having aninner surface configured and adapted to be in substantial clearance of alateral half of the splined shaft 106 and an outer surface defining apair of independent ball bearing tracks 110 formed therein. Each ballbearing track 110 is made up of a load bearing portion 112 and a returnportion 114 interconnected by turnarounds 116. The respective loadbearing portions 112 of each inner portion 108 are located adjacent toone another and are spaced from one another by a dividing member 118.

[0040] Each half segment 102 includes an outer lid portion 120configured to engage inner portion 108 and includes a load bearing plateaperture 122. In the embodiment depicted in FIGS. 6 and 7, engagement ofeach outer lid portion 120 to each inner portion 108 is accomplished bythrough holes 124 formed in the outer lid portion 120 and pegs 126extending from an outer surface of the inner portion 108 configured andadapted to engage the through holes 124. Other engagement mechanisms,such as pins, grooves, adhesives, etc. are also contemplated and arewithin the scope of knowledge of one skilled in the art.

[0041] Each half segment 102 includes a load bearing plate 128dimensioned and configured to fit into the load bearing plate aperture122 of outer lid portion 120 and adapted to be disposed over both loadbearing portions 112 of each ball bearing track 110. The load bearingplate having a central body portion 132 and a pair of longitudinallyextending divergent flat portions 134. An inner surface 130 of the loadbearing plate preferably includes a pair of longitudinal tracks 136which serve as an upper surface of the load bearing portion 112 of theball track 110.

[0042] Meanwhile, the outer surface 132 of the load bearing plate 128 isconfigured and adapted to engage a biasing spring 138. The biasingspring 138 includes a elongate body portion 140 and a pair of elongatediverging corrugated leaf portions 142. The diverging leafs 142 of thebiasing spring 138 are configured and oriented such that each leafportion 142 engages a respective divergent flat portion 134 of the loadbearing plate 128. A plurality of bearing balls 144 are positioned ineach ball bearing track 110 and, when in the load bearing portion 112,serve to transmit loads from the load bearing plates to the splinedshaft 106 as well as to facilitate reciprocal longitudinal motiontherealong. The housing 104 includes a pair of opposed “V” shapedprotrusions 146 extending inwardly from an inner surface thereof andconfigured and adapted to engage an outer surface of the elongate bodyportion 140 of each biasing spring 138. The “V” shaped protrusionpresses the biasing spring 138 such that the diverging leaf portions 142press against the divergent flat portion 134 of the outer surface ofload bearing plate 128.

[0043] In use, each biasing spring 138 applies a pre-load to the bearingballs 144 through each diverging flat portion 134 of the load bearingplate 128. The pre-load being applied at each juncture 148 of the “I”shaped shaft 106 between the pair of horizontal portions 150 and theinterconnecting web portion 152 at an angle “φ” in a range between about25° to about 75° and more preferably about 45°. (See FIG. 6). Onceagain, while the biasing spring 138 is shown as having a pair ofcorrugated leaf springs, it is envisioned that other biasing springs maybe substituted including resilient plastic filler, coil springs, torsionsprings, etc.

[0044] It is envisioned that both the base portion 52 and the lids 74and 78 of the half bearing segment 24 of the first embodiment and theinner portion 108 and outer lid portion 120 of the second embodiment arepreferably formed from an engineering polymer to facilitate ease ofmanufacture.

[0045] To the extent not already indicated, it also will be understoodby those of ordinary skill in the art that any one of the variousspecific embodiments herein described and illustrated may be furthermodified to incorporate features shown in the other specificembodiments.

[0046] The invention in its broader aspects therefore is not limited tothe specific embodiments herein described but departures may be madetherefrom within the scope of the accompanying claims withoutsacrificing its chief advantages.

What is claimed:
 1. A linear motion bearing assembly for movement alonga guide way, a rail or a splined shaft, comprising: a ball retainerstructure formed of a plurality of self-contained ball retainersegments, each of said ball retainer segments including an inner portiondefining at least one ball track having an open load bearing portion, anopen return portion, and turnarounds interconnecting said load bearingand return portions, and an outer lid portion defining a load bearingplate aperture formed therein; a load bearing plate positioned at leastpartially in said load bearing plate aperture of each outer lid portionsuch that said load bearing plate is positioned adjacent said loadbearing portion of said ball track; a plurality of bearing ballsdisposed in said ball tracks for transmitting a load from said shaft tosaid load bearing plate and for facilitating a movement of said linearmotion bearing assembly along said rail; an extended housing retainerstructure enclosing substantially all of an exposed exterior surface ofsaid ball retainer structure and having an inner surface in directcontact with said outer lid portions, said extended housing retainerstructure being configured and dimensioned to maintain said outer lidportions in position and for receiving said load either directly orindirectly from said load bearing plates; and biasing means disposedbetween said bearing plate and said inner surface of said extendedhousing retainer structure, wherein said biasing means extends throughsaid aperture in at least one of said outer lid portions, and whereineach biasing means applies a pre-load to the plurality of bearing ballsdisposed in said ball tracks.
 2. The linear motion bearing assembly ofclaim 1, wherein said ball retainer structure is formed of a pair ofindividual quarter arcuate interengageable self contained ball retainersegments and a half arcuate interengageable self contained ball retainersegments.
 3. The linear motion bearing assembly of claim 2, wherein saidhalf arcuate retainer segment includes a pair of ball tracks and oneload bearing plate.
 4. The linear motion bearing assembly of claim 3,wherein said load bearing portion of each of said pair of ball tracks insaid half arcuate retainer segment are arranged in side-by-sideconfiguration within said half arcuate retainer segment and areseparated from one another by a dividing member formed in said innerportion of said half arcuate retainer segment.
 5. The linear motionbearing assembly of claim 4, wherein said inner portion of said halfarcuate retainer segment is configured and adapted to mate with a splineformed along a length of said shaft.
 6. The linear motion bearingassembly of claim 4, wherein one of said load bearing platessimultaneously engages said load bearing portion of each of said pair ofball tracks.
 7. The linear motion bearing assembly of claim 6, whereinload bearing plate of said half arcuate retainer segment includes a pairof longitudinally extending convergent flat portions configured andadapted to engage said aperture formed in each of said outer lidportions.
 8. The linear motion bearing assembly of claim 7, furthercomprising biasing means disposed between each convergent flat portionof said bearing plate and said inner surface of said extended housingretainer structure, said biasing means extending through said aperturein each of said outer lid portions, wherein each biasing means applies apre-load to the plurality of bearing balls disposed in said pair of balltracks.
 9. The linear motion bearing assembly of claim 8, wherein saidpre-load is applied against opposite sides of said spline at an angle ina range between about 25° to about 75°.
 10. The linear motion bearingassembly of claim 1, wherein said plurality of self-contained ballretainer segments are interengageable.
 11. The linear motion bearingassembly of claim 1, wherein said ball retainer structure is formed of apair of half arcuate interengageable self contained ball retainersegments.
 12. The linear motion bearing assembly of claim 11, whereineach half arcuate retainer segment includes a pair of ball tracks formedtherein.
 13. The linear motion bearing assembly of claim 12, whereinsaid load bearing portion of each of said pair of ball tracks in saidhalf arcuate retainer segment are arranged in side-by-side configurationwithin said half arcuate retainer segment and are separated from oneanother by a dividing member formed in said inner portion of said halfarcuate retainer segment.
 14. The linear motion bearing assembly ofclaim 13, wherein said rail includes a pair of substantially horizontalportions and an interconnecting web portion thereby defining aninterface between said horizontal and said web portions, and whereinsaid inner portion of said half arcuate retainer segment is configuredand adapted to mate with a lateral half of said rail.
 15. The linearmotion bearing assembly of claim 14, wherein said load bearing platessimultaneously engages said load bearing portion of each of said pair ofball tracks.
 16. The linear motion bearing assembly of claim 15, whereineach of said load bearing plates includes a central body portion, a pairof longitudinally extending divergent flat portions, an outer surface,an inner surface oriented to be fit into said load bearing plateaperture, and a pair of longitudinally extending tracks formed alongsaid inner surface, which pair of tracks serve as an upper surface ofsaid load bearing portions of said ball bearing tracks.
 17. The linearmotion bearing assembly of claim 16, further comprising biasing meansdisposed between said outer surface of each of said load bearing platesand said inner surface of said extended housing retainer structure,wherein said biasing means includes an elongate body portion and a pairof elongate diverging corrugated leaf portions configured and adapted toengage said outer surface of said pair of divergent flat portions ofeach of said bearing plates, said biasing means applying a pre-load tothe plurality of bearing balls in said load bearing portion of said pairof ball tracks.
 18. The linear motion bearing assembly of claim 17,wherein said pre-load is applied to said bearing balls along saidinterface between said horizontal portion and said web portion of saidsplined shaft at an angle in a range between about 25° to about 75°. 19.The linear motion bearing assembly of claim 17, wherein said housingretainer structure includes a pair of V-shaped projections extendinginwardly from an inner surface of said housing structure, and whereineach protrusion engages an outer surface of said biasing means which inturn presses into said load bearing plates thereby transmitting saidpre-load to said bearing balls and against said interface in said rail.20. A linear motion bearing assembly for movement along a rail, the railincluding an upper and a lower portion interconnected by a web portionwith the upper and lower portions having a width greater than the webportion, the linear motion bearing assembly, comprising: a ball retainerstructure formed of a pair of half arcuate self-contained ball retainersegments, each of said pair of half arcuate ball retainer segmentsincludes an inner portion defining a pair of ball bearing tracks andhaving an inner surface configured and adapted to mate with a lateralsurface of said rail, with each ball bearing track having an open loadbearing portion, an open return portion, and turnarounds interconnectingsaid load bearing and return portions, wherein each load bearing portionof each ball bearing track is disposed adjacent to one another; an outerlid portion defining a load bearing plate aperture formed therein; aload bearing plate having a central body portion, a pair oflongitudinally extending divergent flat portions, an outer surface, aninner surface oriented to be fit into said load bearing plate aperture,and a pair of longitudinally extending tracks formed along said innersurface, which pair of tracks serve as an upper surface of said loadbearing portions of said ball bearing tracks; a plurality of bearingballs disposed in each of said pair of ball bearing tracks fortransmitting a load from said rail to said load bearing plate and forfacilitating a movement of said linear motion bearing assembly alongsaid rail; an extending housing retainer structure including a pair ofV-shaped projections extending inwardly from an inner surface of saidhousing structure; and biasing means having an elongated body portionand a pair of elongate corrugated leaf portions, said biasing meansbeing disposed between said outer surface of each of said load bearingplates and said V-shaped projections of said housing retainer structure,wherein V-shaped projections press into said biasing means therebyapplying a pre-load to said plurality of bearing balls in said loadbearing portion of said pair of ball tracks which in turn press intosaid rail at each juncture between said upper and lower portions andsaid web portion.